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Does multiple scaling cause resolution loss?


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error404

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Hello everyone,

I had an 18MP picture (3456x5184 pixles) and I was trying to fit it into an A1 canvas of a 100 dpi so I used free transformation to scale it down. Later on, I have decided to make the canvas of 150 dpi instead of 100. Would increasing the resolution now make my picture look pixelated on the canvas? I know that the original photo would look alright on a 150 dpi.
I'm using photoshop CS2.

Many thanks,
 
Try it...I suspect you will not be happy. You did use a copy of the original image ?......??
 
MikeMc said:
Try it...I suspect you will not be happy. You did use a copy of the original image ?......??
Click to expand...

I tried to do this before posting this question, and -contrary to your expectations- I could not see any difference in the photo on the computer screen. I am not sure what can happen in printing, and this is exactly why I am asking :)
 
Here we go with the age old story. What you see on your screen to what is going to print may end being something unexpected. This is because you have two hardware devices here that present data to you in different ways. Looking at your image on screen, nothing matters except pixels period. The dpi or ppi number is simply that, just a number as far as your screen goes. Now, on the other hand, a typical desktop printer is going to want 250 - 300 dpi. So, all your talk of the dpi doesn't mean anything. The print size for your 3456 x 5184 image will provide you with a 11.52" x 17.28 image at 300 dpi. So, if you are using an A1 size, which is 23.4 x 33.1 that's a 100% larger than what you have, so it can't be optimal from the printer.
 
I presume the reason u are asking is because u either lost or discarded the original, or is it because u just don't want to go through all the processing steps at the new rez, right?

Unfortunately, I can think of several different processing schemes that wud accomplish what u described, but would present different challenges, so I can't say with absolute certainty, but my guess is that u won't see much degradation when u up-Rez from 100 to 150 ppi if people view your large print from a reasonable distance, say, over 2 ft away.

T
 
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Tom is exactly right. All I am saying is that your not at the optimum quality your printer can provide. Viewing distance is a definite factor. That size will need a wide format printer and would be a sophisticated machine. Quality should be good.

Sent from my DROID RAZR HD using Tapatalk 2
 
error404 said:
I tried to do this before posting this question, and -contrary to your expectations- I could not see any difference in the photo on the computer screen. I am not sure what can happen in printing, and this is exactly why I am asking :)
Click to expand...


As ALB stated what you SEE is not what you print....follow the advice, and look at some (many) of Toms replies and you will understand screen rgb and printed images
 
what you see can be what you get if you go to view> actual pixel or print view

if you have a 100 dpi image and convert it to 150 dpi you will get a 1.5 x magnification because for every inch adobe will calculate an extra 50 pixels based on the colours around those pixels making it a softer image hard lines will begin to get blurred.

Under default screen view it is based on your monitors pixels you really need to look at actual pixels or print pixels you will see it will enlarge on your screen. I am not sure if cs2 will auto expand your canvas to fit the new dpi or if it will crop it or worse distort it.

so before you send it to print I highly recommend looking at your image through the different views. screens will not show much difference between 72 dpi and 500 dpi in quality to your eye because standard monitors are not capable of seeing beyond that. It is easy to downgrade dpi with more success than it is to increase dpi. This is why you should start with the end product dpi rather than changing it half way through. admittedly a jump from 100 to 150 dpi wont be effected as much as jumping from 72 dpi to 300. but as you say printing on a canvas which will bleed every pixel slightly anyway dont just assume because it looks ok on your screen it will look ok in print.
 
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